Morton's Neuroma

Morton's neuroma (interdigital neuroma, Morton's metatarsalgia) is a compression neuropathy of the common digital nerve and a common cause of forefoot pain. The name is a misnomer: the lesion is not neoplastic, and interdigital nerve compression or perineural fibrosis is the more accurate term. It is named after Thomas Morton (1876), although Durlacher described it earlier, in 1845.

Who. Morton's neuroma accounts for 30% of patients with forefoot pain. Women outnumber men 8:1 (high heels, narrow shoes), the 4th to 6th decades are most commonly affected, and 15-20% of patients have bilateral involvement.

Where. The third web space is the usual site, not the second:

• 3rd web (between the 3rd and 4th metatarsals) - 65%
• 2nd web (between the 2nd and 3rd metatarsals) - 30%
• 4th web - 3%, rare
• 1st web - 2%, very rare

More than one web space is involved in 2-3%.

The nerve. The common digital nerves are branches of the medial and lateral plantar nerves. Each passes beneath the transverse metatarsal ligament and divides into proper digital nerves to the adjacent toes.

Why the third web. The nerve to the third web space receives branches from both the medial and the lateral plantar nerves. At this junction the nerve is thicker and more tethered, so it is less mobile and more susceptible to compression.

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Compression. The nerve passes between the metatarsal heads, where it is compressed against the transverse metatarsal ligament above it and squeezed from the sides by the metatarsal heads. Toe extension stretches it.

Histology. The excised nerve shows:

• Perineural fibrosis
• Demyelination and axonal degeneration
• Renaut bodies (subperineurial fibrosis)
• Endoneurial and epineurial fibrosis
• Small vessel thrombosis and arteriolar thickening

Risk factors.

• Footwear - high heels, which transfer weight forward, and a narrow toe box
• Foot type - pes planus, a hypermobile first ray
• Activities with repetitive forefoot loading - running, ballet
• Anatomy - long metatarsals, a tight intermetatarsal space

The pain. Burning, shooting or electric-shock-like pain in the plantar aspect of the web space, radiating to the adjacent toes (the 3rd and 4th in a third-web neuroma), with tingling or numbness in those toes. Tight shoes, high heels, walking and prolonged standing aggravate it; removing the shoes, massaging the forefoot and rest relieve it.

How much the history is worth. In the diagnostic systematic review by Pitcher et al, the classic "walking on a pebble" sensation and burning pain performed poorly, both close to a coin toss, and should not be leaned on.

Red flags for another diagnosis.

• Night pain - consider tumour or infection
• Swelling - synovitis, gout
• Constitutional symptoms
• Multiple toe involvement - peripheral neuropathy

Mulder's test is the key examination.

1. Hold the foot with one hand around the metatarsal heads
2. Apply lateral compression, squeezing the metatarsals together
3. With the other hand, press the affected web space from plantar to dorsal
4. Positive: a palpable or audible click with reproduction of the symptoms

Reading the click. Mulder's test is highly specific with variable sensitivity: reported sensitivity is 62-98% and specificity 95%. A click is the rule-in finding, with specificity about 0.96 and a positive likelihood ratio of 13 in the Pitcher review; that is powerful when present, but it is not pathognomonic, and a negative click does not exclude the diagnosis. The 0.96 came from clicking reported by the patient, which is not interchangeable with the click the examiner elicits.

What the click is. Transverse compression displaces the hypoechoic web-space lesion superficially between the adjacent metatarsal heads, and that movement is the palpable click. It is also why symptom reproduction, not sound alone, makes the test meaningful.

The rule-out test. The web space compression test, direct pressure on the affected web space from plantar and dorsal, reproduces the symptoms and is less specific than Mulder's. The best rule-out test in the Pitcher review was the modified web space tenderness test, a thumb-index web space squeeze: sensitivity 0.96 and a negative likelihood ratio of 0.04, so a negative squeeze makes Morton's neuroma unlikely.

Sensation. The adjacent toes may have reduced sensation and two-point discrimination may be abnormal, but sensation is often normal early in the disease.

Differential diagnosis. Against metatarsalgia and MTP synovitis:

Other causes of forefoot pain to exclude:

• Stress fracture - point tenderness over bone, swelling
• Freiberg's disease - AVN of the 2nd metatarsal head, adolescent female
• Plantar plate injury - MTP instability, positive drawer test
• Peripheral neuropathy - multiple toes, bilateral

A clinical diagnosis. A positive Mulder's click with classic symptoms is often sufficient to make the diagnosis and start conservative treatment. Imaging is not always required when the presentation is classic; it confirms the diagnosis or excludes other pathology.

Ultrasound. The neuroma is a hypoechoic, ovoid mass in the web space, often at the level of the metatarsal heads, and dynamic compression may demonstrate it. The typical sonographic appearance of fibrotic interdigital nerve enlargement is a well-defined, homogeneous hypoechoic nodule without Doppler flow. Ultrasound is widely available, low cost, radiation-free and dynamic, but operator-dependent. On pooled data it detects neuromas as well as MRI does and is the more cost-effective first-line test (Bignotti et al).

Size. Lesions more than 5mm are significant, and correlation with symptoms improves with size.

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MRI. Indicated for an atypical presentation, after failed treatment to exclude other pathology, and for preoperative planning of large or recurrent neuromas. The lesion lies between the metatarsal heads and is low to intermediate signal on T1 and low signal on T2, from the fibrosis.

Neuroma or bursitis. The deep transverse metatarsal ligament is the landmark. A Morton's neuroma is centred plantar to it, stays low signal on T1 and T2 and enhances after contrast. Intermetatarsal bursal distension occupies the dorsal side and may extend around the narrow interval, so bursitis extends both dorsally and plantarly; it is predominantly T2 hyperintense with peripheral enhancement and looks fluid-like on ultrasound.

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Diagnostic injection. Local anaesthetic injected into the web space: relief confirms the diagnosis, and it can be combined with corticosteroid as treatment.

The ladder. Footwear, a metatarsal pad, then injection, with a conservative trial of 3-6 months before surgery. Overall, 30-40% achieve adequate relief with conservative treatment and 60-70% eventually need surgery.

ConservativeSurgicalOutcomes

Shoes. A wide toe box is the most important change, with a low heel (under 2.5cm), a soft cushioned sole and no pointed shoes.

Metatarsal pad. Placed proximal to the metatarsal heads, the pad spreads the metatarsals apart and reduces nerve compression. Shoe modification with a pad gives improvement in 50-60%.

NSAIDs give short-term symptom relief and do not modify the disease.

Corticosteroid injection. Injected into the web space from dorsal, it gives long-term relief in 30-40%, and a temporary response is common. Multiple injections increase the risk of fat pad atrophy; a maximum of 3 is recommended.

What the steroid adds. The two randomised trials disagree: Thomson found benefit over local anaesthetic at three months, Lizano-Diez found none. The 2024 Cochrane review pools both and finds little to no difference in pain from adding corticosteroid, which brings skin atrophy, hypopigmentation and fat pad atrophy with it. What does improve the injection, at moderate certainty, is ultrasound guidance.

Indications.

• Failed conservative management (3-6 months)
• Significant functional limitation
• Patient preference

Choosing the incision. The dorsal approach is the most common and most surgeons' preference; the plantar approach gives better visualisation. The 2024 Cochrane review has not demonstrated a difference between them.

Dorsal approach.

1. Longitudinal incision between the metatarsal heads
2. Divide the transverse metatarsal ligament
3. Identify the nerve and trace it proximally
4. Excise the neuroma proximal to the metatarsal heads
5. Allow the nerve to retract into the soft tissue

It avoids a plantar scar and allows early weight-bearing. The cost is limited visualisation and the need to divide the transverse ligament.

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Plantar approach. A longitudinal incision over the web space on the sole gives direct access and excellent visualisation, and the nerve is easily identified. The price is a scar on the weight-bearing surface: a painful plantar scar, a risk of hypertrophic scarring, and protected weight-bearing afterwards.

Technical points.

• Excise at least 3cm of nerve
• Cut the nerve in muscle or fat to allow proximal retraction
• Avoid leaving the cut end in a high-pressure zone
• Send the specimen for histology to confirm the diagnosis

The resected specimen includes the common digital nerve and its enlarged segment distal to the bifurcation.

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Results. Quote 76.5% good or excellent at a mean of 15 years (Kasparek, 98 feet). About 74% is the figure usually quoted for primary excision, and one 10-year series reports 61% satisfaction. Satisfaction is quoted more broadly at 75-90%, with complete relief in 50-60%, significant improvement in a further 25-30%, and failure or recurrence in 10-20%.

Recovery. Normal shoes at 4-6 weeks and sport at 6-8 weeks; the final result takes 3-6 months.

Predictors of a good outcome.

• Positive Mulder's click
• Single web space involvement
• Imaging-confirmed lesion more than 5mm
• Classic symptom pattern

How much the numbness matters. In Kasparek's 15-year series it was present in 72% of feet and did not influence satisfaction, but 2 of 13 patients in Lee's 10-year series found it disabling.

Stump neuroma is the most common surgical complication: symptomatic regrowth at the cut nerve end, presenting as recurrent or persistent symptoms. Every poor result in the largest long-term series had one. Management is revision excision with more proximal resection into the plantar fat pad.

Plantar scar. Specific to the plantar approach, the scar is painful with weight-bearing and difficult to treat. Quoted rates vary, from the 5-8% in the table to 10-15%.

Wound problems and CRPS. Infection, dehiscence and delayed healing. Complex regional pain syndrome is rare but serious, with disproportionate pain post-operatively.

Global Epidemiology

• One of the commonest causes of forefoot neuralgia worldwide; strongly associated with constrictive footwear and elevated heels
• Marked female predominance (commonly quoted around 8:1) across populations; peak in the 4th-6th decades
• 3rd web space dominates, followed by the 2nd; multiple/bilateral involvement in a minority
• Lower reported prevalence in habitually barefoot or wide-footwear populations, supporting a footwear-driven mechanical aetiology

Guidelines & Society Positions (Side by Side)

Registry & Evidence Notes

• No dedicated implant registry applies (no implant is used); evidence is driven by RCTs (steroid injection) and surgical case series rather than arthroplasty-style registries
• Imaging meta-analysis confirms ultrasound is equivalent to MRI for detection and is the more cost-effective first-line test
• Economic modelling supports an injection-first pathway (steroid then alcohol) before surgery when conservative measures fail

High- vs Limited-Resource Practice Variation

• Well-resourced settings: ultrasound-guided diagnosis and injection, day-case dorsal neurectomy, MRI for atypical/recurrent cases
• Limited-resource settings: clinical diagnosis with Mulder's sign and footwear/padding emphasised; diagnostic local-anaesthetic injection substitutes for advanced imaging; surgery reserved for refractory disease
• Workforce: depending on jurisdiction, surgery is performed by orthopaedic foot-and-ankle surgeons or, where licensed, podiatric surgeons; complex/revision cases are typically referred to specialist foot-and-ankle units

Multiple neuromas. MRI helps preoperative planning, surgery may need to be staged, and the risk of complications is higher.

Recurrent neuroma. Causes of recurrent symptoms after excision:

• Stump neuroma, the most common
• Incomplete excision
• A missed neuroma in the adjacent web space

Confirm the diagnosis with MRI or a diagnostic injection, and try conservative measures first. Revision surgery resects the nerve more proximally, and a plantar approach can be considered for better visualisation.

MTP instability and the atypical neuroma. MTP instability can deviate the interdigital nerve and bend it against the distal edge of the deep transverse metatarsal ligament, adding focal traction and compression. The nerve then takes a non-standard course, which changes both the exposure and the differential diagnosis. In the reported case shown below, the nerve and neuroma were displaced dorsally and bore a central impression from the adjacent metatarsal heads. A neuroma in an atypical position should prompt assessment for MTP instability rather than automatic attribution to a routine plantar lesion.

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Alcohol sclerosing injection. Dilute ethanol is neurotoxic: it produces chemical (Wallerian) degeneration of the common digital nerve, in effect a "chemical neurectomy" without an incision. Under ultrasound guidance, dilute ethanol (commonly around 20-30%, mixed with local anaesthetic) is injected into the web space around the neuroma as a series, often several injections at one-to-two-week intervals.

How well it works. Case series report widely varying success, roughly 60-90% symptom relief, but the systematic review by Matthews et al judged sclerosing-injection studies to be of limited methodological quality, and durable high-level RCT evidence is lacking. Skin and fat-pad injury from extravasation is the key hazard: extravasated alcohol can cause skin necrosis, plantar fat-pad injury or local reactions. Incomplete response and recurrence are common.

Radiofrequency ablation and cryoneurolysis. Radiofrequency ablation lesions the nerve thermally under image guidance and has been reported in small case series with promising short-term relief. Cryoneurolysis freezes the nerve to interrupt conduction, and its evidence is also limited to case series. Both are minimally invasive, sensation-preserving in intent and repeatable, but neither has robust randomised support, so they remain second-line options where surgery is declined or high-risk.

Guidance and coverage. Image guidance is essential to avoid intravascular or digital-artery injury. Ex vivo, the thermal injury after radiofrequency was focal and concentrated near the electrode, with incomplete depth and circumferential coverage, which is why radiofrequency can reduce pain without reliably ablating the whole neuroma. An ex vivo setup demonstrates the target geometry but cannot substitute for confirming complete in-vivo thermal coverage.

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Where they fit. A reasonable trial after failed footwear, pad and steroid, before open surgery: cost-effectiveness modelling (Ross et al) shows that a sequential steroid-then-alcohol injection pathway can be the dominant strategy. They do not replace an accurate diagnosis, so confirm the lesion on ultrasound and exclude adjacent-space or alternative pathology first.

The idea. Decompression (neurolysis) treats Morton's neuroma as an entrapment rather than a mass. Because the condition is fundamentally a compressive neuropathy beneath the transverse metatarsal ligament, dividing that ligament addresses the cause without sacrificing the nerve, which is left in continuity. Gauthier popularised isolated division of the transverse intermetatarsal ligament as a nerve-sparing alternative to excision.

Techniques.

• Open decompression / neurolysis - dorsal incision, division of the transverse intermetatarsal ligament and external neurolysis of the common digital nerve, which is preserved
• Endoscopic decompression of the intermetatarsal nerve (EDIN) - a minimally invasive endoscopic release of the ligament, aiming for quicker recovery and a smaller scar

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Against neurectomy. Decompression preserves toe sensation, so there is no expected numbness, avoids a stump neuroma, and if it fails, neurectomy remains available as salvage. Because the pathological nerve is left in situ, the risk of incomplete relief and recurrence is higher, and it is best suited to earlier disease or smaller lesions where fibrosis is limited. Larger, chronically fibrotic neuromas and clear mass lesions are generally better served by excision; decompression is attractive when preserving sensation is the priority.

• Does corticosteroid add anything over local anaesthetic? The 2013 Edinburgh RCT (Thomson, n=131) showed benefit over anaesthetic at three months; the 2017 double-blind RCT (Lizano-Diez, n=41) found no difference. The 2024 Cochrane review pools both and settles it in the negative — corticosteroid added to local anaesthetic gives little to no difference in pain (MD −6.31 mm, 95% CI −14.23 to 1.61, low certainty) while adding skin atrophy, hypopigmentation and fat pad atrophy. What the same review does support, at moderate certainty, is ultrasound guidance: guided injection beat unguided by −15.01 mm (95% CI −27.88 to −2.14). The live question is therefore not which drug but who holds the probe.
• Neurectomy vs nerve-preserving surgery. Decompression (transverse intermetatarsal ligament release) avoids permanent numbness and stump neuroma but carries a higher recurrence risk; excision sacrifices sensation but is more definitive. The optimal choice is unsettled and patient-specific.
• Dorsal vs plantar incision. The dorsal approach avoids a weight-bearing scar and allows earlier mobilisation; the plantar approach gives superior exposure and, when correctly placed, a low scar-problem rate. There is now one randomised comparison, pooled in the 2024 Cochrane review: at a mean of 34 months it found little to no difference in satisfaction or adverse events (75 participants, low certainty). The complication profiles differ rather than the totals — hypertrophic scarring after plantar incisions, and missed nerve, wound problems and reoperation after dorsal ones. Largely still surgeon preference, but no longer for want of any evidence.
• Size threshold for significance. A commonly cited cut-off is greater than 5mm, but symptoms correlate imperfectly with size and asymptomatic lesions are seen on imaging — imaging should confirm, not drive, the diagnosis.
• Minimally invasive alternatives. Alcohol sclerosing injection, radiofrequency ablation and cryoneurolysis show promise in case series but lack robust RCT support; reported success rates vary widely and reflect heterogeneous protocols.
• Bursa vs nerve. Whether the dominant pain generator is perineural fibrosis or an associated intermetatarsal bursitis is debated, which partly explains variable response to injection placement.

Related pages: Metatarsalgia for the umbrella presentation this sits inside, with Plantar Plate Insufficiency and Lesser MTP Arthritis for the two differentials most often mistaken for it; Metatarsal Stress Fractures and Freiberg Disease for the bony causes of forefoot pain; Tarsal Tunnel Syndrome for the proximal entrapment that can mimic or coexist; and Hallux Valgus for the deformity that crowds the lesser web spaces.